Stereoselectivity in fragmentation and rearrangement of α-hydroxyimino-phosphinates and -phosphonates. A synthetic approach to acylphosphon- and phosphor-amidates. Crystal structures of methyl (E)-α-hydroxyimino-benzylphenylphosphinate and methyl benzoylphenylphosphonamidate

Abstract

Reaction of methyl benzoylphenylphosphinate 1 with hydroxylamine gave methyl α-hydroxy-iminobenzylphenylphosphinate 2 as a mixture of E and Z isomers with the E isomer predominating. Pure (E)-2 when heated gave methyl N-benzoylphenylphosphonamidate 3 as the sole product. In contrast, (Z)-2 when heated gave, as a result of fragmentation, mainly methyl hydrogen phenylphosphonate 4 and benzonitrile, together with methyl N-phenylcarbamoylphenylphosphinate 5 as the minor product; the latter results from Beckmann rearrangement of (Z)-2. Analogous behaviour is exhibited by the two geometrical isomers of dimethyl α-hydroxyiminobenzylphosphonate 8. The crystal structures of methyl (E)-α-hydroxyiminobenzylphenylphosphinate (E)-2 and methyl benzoylphenylphosphonamidate 3 are reported.